We have studied the optical and electrical properties of InGaAlP/InGaP PIN heterostructures by the effects of post-growth annealing, substrate misorientation and growth temperature. For the as-grown p-type In0.5(Ga0.5Al0.5)0.5P, the 15° misoriented sample shows the largest hole concentration of 1 × 1018 cm-3 as compared to 2° and 10° misoriented samples. After annealing at 900°C for 30 s, the hole concentration increases about three times to 2.6 × 1018 cm-3. The increased hole concentration is related to the four times enhanced photoluminescence (PL) intensity. In the In0.6 Ga0.4P/In0.5(Ga0.6Al0.4) 0.5P stained multiple quantum wells, the post-growth annealing also improves the PL integrated intensity. The PL intensity on an as-grown sample decreases with the increased degree of misorientation, while the PL peak energy increases with the increased degree of misorientation, from 0°, 2°, 10° toward 15°. The PL intensities are larger for samples grown at 760°C than those grown at 700°C.